Sorry, language issue. So tonal center is not a correct term, it refers to tonal center of the scale, “resting note” (ok, not a correct term either). But the point still applies. 
I’ll edit it, got a suggestion for the term that I should use
No probs
Tonic is the correct term or ‘key’/‘root’ note. I think I get what you’re trying to say is about inversions:
ie D minor = D F# G (1st inversion), F# G D (2nd inversion) and the fact that you can use notes from different octaves to ‘widen’ the chord
ie
D4 F#4 G4 will sound closer or tighter than D3 F#4 G5. Same chord, same inversion, but bigger spread
Is that what you mean?
Cheers!
I mean that it is possible to sketch the chord sequences from simple melodies by expanding single notes into chords. This allows to sketch harmonic progressions with single notes.
I mean that if the aim is certain progression, but one is uncertain about what notes to put in, it is possible to take one of the approaches I mentioned, and try to build the chord from that point of view.
I mean, that if not thinking strictly in modes or grades or whatever those I-VII are called, it is possible to find the desired width of the chord that matches the desired effect in the chord sequence, for example the melody that highest notes make, or the bass pattern, or desired perceived pitch of the chord, or anything in between. Also the actual width of the chord interval affects the feel of the chord, so especially when making chords with single instrument it can be helpful to play with things like that.
And of course what you said applies too: If you know the chord you need, the chord can be widen or narrowed by varying the octave and inversions. Wider chords also have more room for middle notes, making it easier to go into desired direction.
The points I made should be used as guidelines of course, so incorporating them into any theoretical musical practice should not be a problem.
Isn’t key note of the chord the lowest note in it? Or is it ground note, and key note is tonic? My dictionary gave both key- and ground note for the term.
Or does this post refer to my post at all? Am I making too many questions?
lolz, this damn root note. i’ve only heard the term “root (note)” in connection with chords. http://en.wikipedia.org/wiki/Root_note
this was kind of interesting in that wikipedia entry: Basis in physics & mathematics - The concept of root has some basis in the physical properties of waves. When two notes of an interval from the harmonic series are played at the same time, people sometimes perceive the fundamental note of the interval. For example, if notes with frequency ratios of 7:6 (a septimal minor third) were played, people could perceive a note whose frequency was 1/6th of the lower interval. The following sound file demonstrates this phenomenon, using sine waves, pure and simple waves for which this phenomena is most easily evident
key is kind of a mess of a term imo: In music theory, the term key is used in many different and sometimes contradictory ways. A common use is to speak of music as being “in” a specific key, such as in the key of C or in the key of F-sharp. Sometimes the terms “major” or “minor” are appended, as in the key of A minor or in the key of B-flat major. Although the concept of musical key can be a complicated subject when examined closely, broadly speaking the phrase in key of C means that C is music’s harmonic center or tonic. Note that the letter-name “C” does not indicate a single specificpitch but rather all pitches with the letter name C (sometimes called a pitch class). The terms “major” and “minor” further imply the use of a major scale or a minor scale. Thus the phrase in the key of E major implies a piece of music harmonically centered on the note E and making use of a major scale whose first note, or tonic, is E. Although the term “key” is commonly used this way, actual music can rarely be described so simply.
so it’s basically a loosly defined concept which most often can’t applied to real music. great, cuz music theory isn’t confusey enuf as it is! 